Electricity meters provide a mechanism for utility companies to measure electricity consumption at a residence, business, facility, or other site. Such electricity meters contain metrology to sense and measure electricity consumption at the site. The metrology typically includes one or more hardware components, including sensors, which makes up a metrology device. Various technologies and associated hardware can be used for a metrology device of an electricity meter including shunts, current transformers, Rogowski coils, Hall effect devices, etc.
Particularly, metrology devices that use Hall effect devices (“Hall-based” metrology devices) leverage the Hall effect to allow the metrology device to detect an electric current flowing through one or more electrical conductors. That is, an electrical conductor with a current flowing through it produces a magnetic field that is proportional to the current flowing through the electrical conductor. This magnetic field is detectable by the Hall effect device which generates an output corresponding to the magnetic flux density of the magnetic field.
Electricity meters may be single-phase, bi-phase or poly-phase meters. Hall-based metrology devices typically use a combination of a single Hall effect sensor and a magnetic concentrator, such as a magnetically permeable core (e.g., iron core), for each phase of the electricity meter. The purpose of the magnetic concentrator is to strengthen or concentrate the magnetic field produced by an electrical conductor carrying an electric current, as well as to shield the Hall effect device from external alternating current (AC) fields.
One known drawback of traditional Hall-based metrology devices is that they are susceptible to tampering with a direct current (DC) magnet (sometimes referred to as a DC magnet attack). Specifically, a DC magnet positioned next to the magnetic concentrator can saturate the magnetic concentrator (typically an iron core) so that it degrades the magnetic properties of the material used in the magnetic concentrator. DC magnet attacks results in reduction in measurement accuracy and can potentially cause under-billing based on the electricity meter's measurement of electricity consumption. These types of DC magnet attacks are becoming a serious concern in the utility industry due to the potential for under-billing resulting from tampering with the metrology devices in electricity meters.